In recent years, one of the improvements in electric contact techniques in the semiconductor art has been the development of a wireless bonding method, which is also called the beam lead bonding method. The prior art is represented by, for example, U.S. Pat. No. 3,550,261, which discloses a process wherein electrode pads or contact areas are formed on a semiconductor wafer, the surface of which is partly covered by a protective film, and a conductive selectively adhering material is deposited over the protective film, the conductive material adhering to the contact area but not adhering to the protective film.
However, it is very difficult to deposit a material of such characteristics. Since strict requirements are imposed on the selection of the selectively adhering film, the various conductive metal materials usually employed are not equally applicable to the deposition of such a film.
In addition, as disclosed in U.S. Pat. No. 3,590,478, an oxidation film covering the surface of a semiconductor wafer is selectively etched to expose desired electrode pads or contact areas, and then the surface of the semiconductor wafer except the electrode areas is coated with a photo-resist material. Thereafter, beam leads are formed to extend over the photo-resist film. One of the disadvantages of this prior art method is that the semiconductor wafer cannot be treated at a considerably high temperature because of the use of the photo-resist material. Consequently, it is not possible to obtain beam leads having strong bonding by this technique.